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mbed-dev/platform/SingletonPtr.h@6:0018763974d3, 2017-02-25 (annotated)

Committer:
elmot
Date:
Sat Feb 25 08:59:21 2017 +0000
Revision:
6:0018763974d3
Parent:
1:d0dfbce63a89 
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elmot 1:d0dfbce63a89 1
elmot 1:d0dfbce63a89 2 /** \addtogroup platform */
elmot 1:d0dfbce63a89 3 /** @{*/
elmot 1:d0dfbce63a89 4 /* mbed Microcontroller Library
elmot 1:d0dfbce63a89 5 * Copyright (c) 2006-2013 ARM Limited
elmot 1:d0dfbce63a89 6 *
elmot 1:d0dfbce63a89 7 * Licensed under the Apache License, Version 2.0 (the "License");
elmot 1:d0dfbce63a89 8 * you may not use this file except in compliance with the License.
elmot 1:d0dfbce63a89 9 * You may obtain a copy of the License at
elmot 1:d0dfbce63a89 10 *
elmot 1:d0dfbce63a89 11 * http://www.apache.org/licenses/LICENSE-2.0
elmot 1:d0dfbce63a89 12 *
elmot 1:d0dfbce63a89 13 * Unless required by applicable law or agreed to in writing, software
elmot 1:d0dfbce63a89 14 * distributed under the License is distributed on an "AS IS" BASIS,
elmot 1:d0dfbce63a89 15 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
elmot 1:d0dfbce63a89 16 * See the License for the specific language governing permissions and
elmot 1:d0dfbce63a89 17 * limitations under the License.
elmot 1:d0dfbce63a89 18 */
elmot 1:d0dfbce63a89 19 #ifndef SINGLETONPTR_H
elmot 1:d0dfbce63a89 20 #define SINGLETONPTR_H
elmot 1:d0dfbce63a89 21
elmot 1:d0dfbce63a89 22 #include <stdint.h>
elmot 1:d0dfbce63a89 23 #include <new>
elmot 1:d0dfbce63a89 24 #include "platform/mbed_assert.h"
elmot 1:d0dfbce63a89 25 #ifdef MBED_CONF_RTOS_PRESENT
elmot 1:d0dfbce63a89 26 #include "cmsis_os.h"
elmot 1:d0dfbce63a89 27 #endif
elmot 1:d0dfbce63a89 28
elmot 1:d0dfbce63a89 29 #ifdef MBED_CONF_RTOS_PRESENT
elmot 1:d0dfbce63a89 30 extern osMutexId singleton_mutex_id;
elmot 1:d0dfbce63a89 31 #endif
elmot 1:d0dfbce63a89 32
elmot 1:d0dfbce63a89 33 /** Lock the singleton mutex
elmot 1:d0dfbce63a89 34 *
elmot 1:d0dfbce63a89 35 * This function is typically used to provide
elmot 1:d0dfbce63a89 36 * exclusive access when initializing a
elmot 1:d0dfbce63a89 37 * global object.
elmot 1:d0dfbce63a89 38 */
elmot 1:d0dfbce63a89 39 inline static void singleton_lock(void)
elmot 1:d0dfbce63a89 40 {
elmot 1:d0dfbce63a89 41 #ifdef MBED_CONF_RTOS_PRESENT
elmot 1:d0dfbce63a89 42 osMutexWait(singleton_mutex_id, osWaitForever);
elmot 1:d0dfbce63a89 43 #endif
elmot 1:d0dfbce63a89 44 }
elmot 1:d0dfbce63a89 45
elmot 1:d0dfbce63a89 46 /** Unlock the singleton mutex
elmot 1:d0dfbce63a89 47 *
elmot 1:d0dfbce63a89 48 * This function is typically used to provide
elmot 1:d0dfbce63a89 49 * exclusive access when initializing a
elmot 1:d0dfbce63a89 50 * global object.
elmot 1:d0dfbce63a89 51 */
elmot 1:d0dfbce63a89 52 inline static void singleton_unlock(void)
elmot 1:d0dfbce63a89 53 {
elmot 1:d0dfbce63a89 54 #ifdef MBED_CONF_RTOS_PRESENT
elmot 1:d0dfbce63a89 55 osMutexRelease (singleton_mutex_id);
elmot 1:d0dfbce63a89 56 #endif
elmot 1:d0dfbce63a89 57 }
elmot 1:d0dfbce63a89 58
elmot 1:d0dfbce63a89 59 /** Utility class for creating an using a singleton
elmot 1:d0dfbce63a89 60 *
elmot 1:d0dfbce63a89 61 * @Note Synchronization level: Thread safe
elmot 1:d0dfbce63a89 62 *
elmot 1:d0dfbce63a89 63 * @Note: This class must only be used in a static context -
elmot 1:d0dfbce63a89 64 * this class must never be allocated or created on the
elmot 1:d0dfbce63a89 65 * stack.
elmot 1:d0dfbce63a89 66 *
elmot 1:d0dfbce63a89 67 * @Note: This class is lazily initialized on first use.
elmot 1:d0dfbce63a89 68 * This class is a POD type so if it is not used it will
elmot 1:d0dfbce63a89 69 * be garbage collected.
elmot 1:d0dfbce63a89 70 */
elmot 1:d0dfbce63a89 71 template <class T>
elmot 1:d0dfbce63a89 72 struct SingletonPtr {
elmot 1:d0dfbce63a89 73
elmot 1:d0dfbce63a89 74 /** Get a pointer to the underlying singleton
elmot 1:d0dfbce63a89 75 *
elmot 1:d0dfbce63a89 76 * @returns
elmot 1:d0dfbce63a89 77 * A pointer to the singleton
elmot 1:d0dfbce63a89 78 */
elmot 1:d0dfbce63a89 79 T* get() {
elmot 1:d0dfbce63a89 80 if (NULL == _ptr) {
elmot 1:d0dfbce63a89 81 singleton_lock();
elmot 1:d0dfbce63a89 82 if (NULL == _ptr) {
elmot 1:d0dfbce63a89 83 _ptr = new (_data) T();
elmot 1:d0dfbce63a89 84 }
elmot 1:d0dfbce63a89 85 singleton_unlock();
elmot 1:d0dfbce63a89 86 }
elmot 1:d0dfbce63a89 87 // _ptr was not zero initialized or was
elmot 1:d0dfbce63a89 88 // corrupted if this assert is hit
elmot 1:d0dfbce63a89 89 MBED_ASSERT(_ptr == (T *)&_data);
elmot 1:d0dfbce63a89 90 return _ptr;
elmot 1:d0dfbce63a89 91 }
elmot 1:d0dfbce63a89 92
elmot 1:d0dfbce63a89 93 /** Get a pointer to the underlying singleton
elmot 1:d0dfbce63a89 94 *
elmot 1:d0dfbce63a89 95 * @returns
elmot 1:d0dfbce63a89 96 * A pointer to the singleton
elmot 1:d0dfbce63a89 97 */
elmot 1:d0dfbce63a89 98 T* operator->() {
elmot 1:d0dfbce63a89 99 return get();
elmot 1:d0dfbce63a89 100 }
elmot 1:d0dfbce63a89 101
elmot 1:d0dfbce63a89 102 // This is zero initialized when in global scope
elmot 1:d0dfbce63a89 103 T *_ptr;
elmot 1:d0dfbce63a89 104 // Force data to be 4 byte aligned
elmot 1:d0dfbce63a89 105 uint32_t _data[(sizeof(T) + sizeof(uint32_t) - 1) / sizeof(uint32_t)];
elmot 1:d0dfbce63a89 106 };
elmot 1:d0dfbce63a89 107
elmot 1:d0dfbce63a89 108 #endif
elmot 1:d0dfbce63a89 109
elmot 1:d0dfbce63a89 110 /** @}*/